Yes, my rule of thumb is I try to do a 2 for $20 or sometimes even 3 for $20. A better question to focus on is “what books do I NEED to sell”. If you don’t have the rite book then you will not sell any books. If you have just a real general motivational book then there is a chance you may sell a few but you really have to zero in on the NEED and WANTS of your college audience.
Ex) They want to be the popular kid on campus, they want to become a better student, they want to save money, they want to be a better leader & they want to get a great job.
It all comes down to being able to tie your topic with their wants.
During your talk, mention the ways that your book is going to help them and use real examples. You have to have the rite stuff but most importantly you have to PITCH it the rite way.